High fidelity speaker



Oct. 7, 1969 P. BREVARD 3 4 HIGH FIDELITY SPEAKER Original Filed Nov. 8, 1965 zl-dlhll I7 .LIG J INVENTOR.

United States Patent 3,470,976 HIGH FIDELITY SPEAKER Procter Brevard, 111 Washington Ave.,

Evansville, Ind. 47713 I Continuation of application Ser. No. 506,786, Nov. 8, 1965. This application Dec. 11, 1967, Ser. No. 689,726 Int. Cl. Gk 13/00; H041- 7/18 U.S. Cl. 181-31 1 Claim This is a continuation of application Ser. No. 506,786, filed Nov. 8, 1965.

My invention relates to speakers for high fidelity sound reproduction. An object of the invention is to eifect thorough uniformity of tonality, particularly quality and strength, throughout the audible range of sound reproduced. Another objective is uniform and pleasing timbre and tone color throughout the audible range. ,Still another objective is omnipresence of all the sound reproduced throughout the audible range. Attainment of these objectives while producing full strength of sound at low power input is an important result of my invention.

The single figure of the drawing shows in a side elevational view, partially in vertical section, a speaker embodying the invention.

Referring to the drawing, vertical walls 10 and a partition or diaphragm 11 form an upper cell or chamber 12 and a lower cell or chamber 13. The upper end of chamber 12 is provided with a top or cover 14 having an opening 15. The lower end of chamber 13 is provided with a bottom or cover 16 having a smaller opening 17. The partition 11 is provided with a still smaller opening 18.

A cone type speaker unit 19 is rigidly attached to an aluminum baflle plate 20 which is resiliently supported on the top cover 14 by caulking compound or soft rubber to seal the opening 15 and hold the speaker unit 19 in juxtaposition to that opening.

The walls 10 of the chambers 12 and 13 may be either curvilinear or rectilinear, but the height of chamber 12 is approximately twice the height of chamber 13 and the sum of the heights of chambers 12 and 13 is at least three times any wall-to-wall horizontal dimension in chambers 12 and 13.

The area of opening 18 in the cell separator '11 is onehalf or less than one-half the area of the bottom vent or opening 17.

The walls 10 are preferably composed of material having a natural resonance frequency beyond audible range, meaning above or below the frequencies that people can hear. Examples of materials which I have used 3,470,976 Patented Oct. 7, 1969 include heavy limestone, a light plastic such as foamed polystyrene, and paper sheet rolled upon itself with a silicate binder.

The speaker is provided with legs 21 or a like support structure to elevate the bottom 16 above the supporting surface to permit movement of air in the bottom vent 17.

A speaker constructed substantially as described and illustrated produces all the objectives of the invention when the speaker unit 19 is energized. The double tuning of chambers 12 and 13 with openings 18 and 17, respectively, gives a much more uniform and flat response curve. Low notes become discernible while high and medium range notes are retained at full strength with low power input, and uniform and pleasing timbre and tone color throughout the audible range.

Without limitation by specific embodiments set forth in this description, the invention is defined by the following claim.

I claim:

1. In a speaker for a high fidelity reproduction of sound:

two chambers alike in two dimensions, the third dimension of one chamber being at least twice the third dimension of the other, the sum of the third dimensions of the two chambers being at least three times any of the two dimensions,

a first opening into said one chamber,

a diaphragm type speaker mounted in said first open- 8, a second smaller opening into said other chamber, and a third opening connecting said chambers and being not more than one-half the area of said second openmg.

References Cited UNITED STATES PATENTS 1,837,755 12/1931 Carlisle et a1. 181-31 2,097,289 10/ 1937 Olson 181-3 1 2,233,459 3/ 1941 Shoup et a1. 18131 2,881,850 4/1959 Bonn 181-31 FOREIGN PATENTS 971,517 7/1950 France. 143,597 9/ 1951 Australia. 1,201,682 7/1959 France.

980,670 1/1965 Great Britain.

STEPHEN J. TOMSKY, Primary Examiner 

1. IN A SPEAKER FOR A HIGH FIDELITY REPRODUCTION OF SOUND: TWO CHAMBERS ALIKE IN TWO DIMENSIONS, THE THIRD DIMENSION OF ONE CHAMBER BEING AT LEAST TWICE THE THIRD DIMENSION OF THE OTHER, THE SUM OF THE THIRD DIMENSIONS OF THE TWO CHAMBERS BEING AT LEAST THREE TIMES ANY OF THE TWO DIMENSIONS, A FIRST OPENING INTO SAID ONE CHAMBER, 